Year II of this project will focus on the implementation of protocol IV of the original proposal. The specific aim of this protocol is to study the amplitude and phase relations of CSF pulse waveforms as they are affected by two pertubations: alterations of the container property of the brain and the establishment of active hydrocephalus. The instrumentation necessary to conduct this phase of research is currently on site and consists of: 1) An FM-instrumentation tape recorder for capture and storage of pulse wave signals from experimental subjects; 2) analog to digital conversion of these signals; and PDP 11/23 computer for analysis of this data. Signal analysis will be performed in both time and frequency domains. Software is currently being developed for the fast Fourier transform of these signals (the method used to enter the frequency domain from the time domain) and will be operational before year II begins. Pulse waves will be sampled at ventricle, cisterna magna and convexity subarachnoid cerebrospinal fluid spaces, as well as sagittal sinus and carotid artery (via lingual artery catheterization). Respiratory components will be filtered. The analysis of these pulse waveforms will be conducted in 4 conditions: 1) The intact animal; 2) craniectomy, 3) durectomy (i.e., conditions 2 and 3 representing altered container properties) and 4) The hydrocephalic state. Changes in these signals will also be investigated during pertubations of cerebrospinal fluid. The objectives of data analysis will include the determination of the phase and amplitude relationships of CSF pulses as container properties of the brain are altered and during ventricular enlargement. The hypothesis to be tested is that transient pressure gradients created by phase and amplitude changes in the CSF pulse accompany progressive ventricular enlargement in hydrocephalus.